Across countryside, non-food crops are growing alongside wheat．Some are used in new alternatives to plastics and other materials, but others will simply be burned． Burning crops is becoming more popular because it is good for the planet．Doing so is also cheaper than burning fossil fuels．As more land is devoted to non-food crop production, the economics of crops for fuel are likely to become even more favorable． Humans have been burning such biomass—organic materials from plants or animals— since they discovered fire．But that burning fossil fuels could have catastrophic consequences has brought biomass back into fashion． Even allowing for emissions (排放) of carbon dioxide from fuel used in planting, harvesting, processing and transporting biomass fuel, replacing fossil fuel with biomass can typically reduce greenhouse gas emissions by more than 90 percent． Power stations around the world are experimenting with forms of biomass to add to their coal or oil, with encouraging results．Indeed, power companies could profit by turning to biomass, especially when the subsidies (补助) many governments offer for using renewable energy are taken into account． Farmers can benefit from growing biomass．In Europe, the reduction of subsidies for certain crops is exposing farmers to market forces．Instead of being paid for whatever they produce, farmers must seek a clear demand for their product．Many believe that the demand for alternatives to fossil fuels could be just such a driver． But while biomass offers a variety of potential alternatives, the world's infrastructure (基础设施） has developed around burning fossil fuels to such a stage that switching to biomass involves a change in conception that many companies have not accepted． Also, there are problems with using biomass．Although most coal-fired power stations could take a small amount of their fuel from biomass without significant adjustment, few are built to run on biomass alone．Burning some forms of biomass also causes environmental problems．Oils and waste can be smelly, while wood produces smoke unless burned properly． The supply chains for fossil fuels are set up well, but those for biomass are just the beginning. Sources of supply for biomass rely on farm production and can therefore be less reliable. They are necessarily limited and it wouldn't make sense to turn a very large amount of valuable agricultural land away from food crops．But as the world adjusts to the need to control greenhouse gas emissions, these problems may receive more attention． 小题1:What do we know about biomass?
a．It gives off less greenhouse gases． b．It helps farmers receive subsidies for what they produce． c．It has met the clear demand for energy． d．It has brought subsidies for some power companies． e．It is cheaper than burning fossil fuels．
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